Conventionally, an image forming apparatus of an electrophotographic type such as an electrophotographic copying machine uses a developer of fine particles. In such an image forming apparatus, the developer is supplied from the developer supply container in response to consumption thereof resulting from image forming operation.
As for the conventional developer supply container, an example is disclosed in Japanese Laid-Open Utility Model Application Sho 63-6464.
In the apparatus disclosed in Japanese Laid-Open Utility Model Application Sho 63-6464, the developer is let fall all together into the image forming apparatus from the developer supply container. More particularly, in the apparatus disclosed in Japanese Laid-Open Utility Model Application Sho 63-6464, a part of the developer supply container is formed into a bellow-like portion so as to permit all of the developer can be supplied into the image forming apparatus from the developer supply container even when the developer in the developer supply container is caked. More particularly, in order to discharge the developer caked in the developer supply container into the image forming apparatus side, the user pushes the developer supply container several times to expand and contract (reciprocation) the bellow-like portion.
Thus, with the apparatus disclosed in Japanese Laid-Open Utility Model Application Sho 63-6464, the user has to manually operate the bellow-like portion of the developer supply container.
On the other hand, Japanese Laid-open Patent Application 2002-72649 employs a system in which the developer is automatically sucked from the developer supply container into the image forming apparatus using a pump. More particularly, a suction pump and an air-supply pump are provided in the main assembly side of the image forming apparatus, and nozzles having a suction opening and an air-supply opening, respectively are connected with the pumps and are inserted into the developer supply container (Japanese Laid-open Patent Application 2002-72649, FIG. 5). Through the nozzles inserted into the developer supply container, an air-supply operation into the developer supply container and a suction operation from the developer supply container are alternately carried out. Japanese Laid-open Patent Application 2002-72649 states that when the air fed into the developer supply container by the air-supply pump passes through the developer layer in the developer supply container, the developer is fluidized.
Thus, in the device disclosed in Japanese Laid-open Patent Application 2002-72649, the developer is automatically discharged, and therefore, the load in operation imparted to the user is reduced, but the following problems may arise.
More particularly, in the device disclosed in Japanese Laid-open Patent Application 2002-72649, the air is fed into the developer supply container by the air-supply pump, and therefore, the pressure (internal pressure) in the developer supply container rises.
With such a structure, even if the developer is temporarily scattered when the air fed into the developer supply container passes through the developer layer, the developer layer results in being packed again by the rise of the internal pressure of the developer supply container by the air-supply.
Therefore, the flowability of the developer in the developer supply container decreases, and in the subsequent suction step, the developer is not easily discharged from the developer supply container, with the result of shortage of the developer amount supplied.